Buggy code:
public abstract class BeanUtils { private static final Log logger = LogFactory . getLog ( BeanUtils . class ) ; private static final Map < Class < ? > , Boolean > unknownEditorTypes = Collections . synchronizedMap ( new WeakHashMap < Class < ? > , Boolean > ( ) ) ; public static < T > T instantiate ( Class < T > clazz ) throws BeanInstantiationException { } public static < T > T instantiateClass ( Class < T > clazz ) throws BeanInstantiationException { } @ SuppressWarnings ( "unchecked" ) public static < T > T instantiateClass ( Class < ? > clazz , Class < T > assignableTo ) throws BeanInstantiationException { } public static < T > T instantiateClass ( Constructor < T > ctor , Object ... args ) throws BeanInstantiationException { } public static Method findMethod ( Class < ? > clazz , String methodName , Class < ? > ... paramTypes ) { } public static Method findDeclaredMethod ( Class < ? > clazz , String methodName , Class < ? > ... paramTypes ) { } public static Method findMethodWithMinimalParameters ( Class < ? > clazz , String methodName ) throws IllegalArgumentException { } public static Method findDeclaredMethodWithMinimalParameters ( Class < ? > clazz , String methodName ) throws IllegalArgumentException { } public static Method findMethodWithMinimalParameters ( Method [ ] methods , String methodName ) throws IllegalArgumentException { } public static Method resolveSignature ( String signature , Class < ? > clazz ) { } public static PropertyDescriptor [ ] getPropertyDescriptors ( Class < ? > clazz ) throws BeansException { } public static PropertyDescriptor getPropertyDescriptor ( Class < ? > clazz , String propertyName ) throws BeansException { } public static PropertyDescriptor findPropertyForMethod ( Method method ) throws BeansException { } public static PropertyEditor findEditorByConvention ( Class < ? > targetType ) { } public static Class < ? > findPropertyType ( String propertyName , Class < ? > ... beanClasses ) { } public static MethodParameter getWriteMethodParameter ( PropertyDescriptor pd ) { } public static boolean isSimpleProperty ( Class < ? > clazz ) { } public static boolean isSimpleValueType ( Class < ? > clazz ) { } public static void copyProperties ( Object source , Object target ) throws BeansException { } public static void copyProperties ( Object source , Object target , Class < ? > editable ) throws BeansException { } public static void copyProperties ( Object source , Object target , String ... ignoreProperties ) throws BeansException { } private static void copyProperties ( Object source , Object target , Class < ? > editable , String ... ignoreProperties ) throws BeansException { Assert . notNull ( source , "Source<seq2seq4repair_space>must<seq2seq4repair_space>not<seq2seq4repair_space>be<seq2seq4repair_space>null" ) ; Assert . notNull ( target , "Target<seq2seq4repair_space>must<seq2seq4repair_space>not<seq2seq4repair_space>be<seq2seq4repair_space>null" ) ; Class < ? > actualEditable = target . getClass ( ) ; if ( editable != null ) { if ( ! ( editable . isInstance ( target ) ) ) { throw new IllegalArgumentException ( ( ( ( ( "Target<seq2seq4repair_space>class<seq2seq4repair_space>[" + ( target . getClass ( ) . getName ( ) ) ) + "]<seq2seq4repair_space>not<seq2seq4repair_space>assignable<seq2seq4repair_space>to<seq2seq4repair_space>Editable<seq2seq4repair_space>class<seq2seq4repair_space>[" ) + ( editable . getName ( ) ) ) + "]" ) ) ; } actualEditable = editable ; } PropertyDescriptor [ ] targetPds = BeanUtils . getPropertyDescriptors ( actualEditable ) ; List < String > ignoreList = ( ignoreProperties != null ) ? Arrays . asList ( ignoreProperties ) : null ; for ( PropertyDescriptor targetPd : targetPds ) { Method writeMethod = targetPd . getWriteMethod ( ) ; if ( ( writeMethod != null ) && ( ( ignoreProperties == null ) || ( ! ( ignoreList . contains ( targetPd . getName ( ) ) ) ) ) ) { PropertyDescriptor sourcePd = BeanUtils . getPropertyDescriptor ( source . getClass ( ) , targetPd . getName ( ) ) ; if ( sourcePd != null ) { Method readMethod = sourcePd . getReadMethod ( ) ; <START_BUG> if ( ( readMethod != null ) && ( writeMethod . getParameterTypes ( ) [ 0 ] . isAssignableFrom ( readMethod . getReturnType ( ) ) ) ) { <END_BUG> try { if ( ! ( Modifier . isPublic ( readMethod . getDeclaringClass ( ) . getModifiers ( ) ) ) ) { readMethod . setAccessible ( true ) ; } Object value = readMethod . invoke ( source ) ; if ( ! ( Modifier . isPublic ( writeMethod . getDeclaringClass ( ) . getModifiers ( ) ) ) ) { writeMethod . setAccessible ( true ) ; } writeMethod . invoke ( target , value ) ; } catch ( Throwable ex ) { throw new FatalBeanException ( ( ( "Could<seq2seq4repair_space>not<seq2seq4repair_space>copy<seq2seq4repair_space>property<seq2seq4repair_space>'" + ( targetPd . getName ( ) ) ) + "'<seq2seq4repair_space>from<seq2seq4repair_space>source<seq2seq4repair_space>to<seq2seq4repair_space>target" ) , ex ) ; } } } } } } }

Fix:
if ( ( readMethod != null ) && ( ClassUtils . isAssignable ( writeMethod . getParameterTypes ( ) [ 0 ] , readMethod . getReturnType ( ) ) ) ) {